Oh, there's an entire list of reasons why he could have left. It could have been something you did. Example: My friend dated a girl for several years, and she started asking about getting married. He's not even out of college yet, but she finally gave him a choice: "If you haven't decided in five years that you want me, then we're done." He snapped and shouted, "I don't EVER want to get married!" That was the end of that. Except it's not, because they're "sort of" dating again.
It could be something he did. Guys lie. He may have found someone else. Example: Been dating for several years, the novelty has worn off. Suddenly, a new girl walks on the scene. New mysteries, new adventures, new passion.
You are both still very young, and if you're twenty now, and you've dated for 4 years, I'm assuming you started dating when you were sixteen. People change, and during that age, people change a LOT. It's very possible that, as hard and cold as this sounds, he just lost interest. Brain still developing, personality changing. And I don't want to sound mean, but you're line of "People say we are both young being 20 years old. But that is not an excuse to leave a devoted woman," sounds slightly controlling. I read that and I instantly hear a woman yelling it at me. The type of woman who cared for her husband greatly, but bossed him around the house and brow beat him, like some of those women from the old T.V. shows.
Give it some time. It is possible that he will come back around and realize what he had and then ask for you back. Whether you take him back is entirely up to you.
